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<Title>back_insert_iterator&lt;BackInsertionSequence&gt;</Title>
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<H1>back_insert_iterator&lt;BackInsertionSequence&gt;</H1>

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<TD Align=left><Img src = "iterators.gif" Alt=""   WIDTH = "194"  HEIGHT = "38" ></TD>
<TD Align=right><Img src = "type.gif" Alt=""   WIDTH = "194"  HEIGHT = "39" ></TD>
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<TD Align=left><Img src = "adaptors.gif" Alt=""   WIDTH = "194"  HEIGHT = "38" ></TD>
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<TD Align=left VAlign=top><b>Categories</b>: iterators, adaptors</TD>
<TD Align=right VAlign=top><b>Component type</b>: type</TD>
</TR>
</Table>

<h3>Description</h3>
<tt>Back_insert_iterator</tt> is an iterator adaptor that functions as an
<A href="OutputIterator.html">Output Iterator</A>: assignment through a <tt>back_insert_iterator</tt> inserts
an object after the last element of a <A href="BackInsertionSequence.html">Back Insertion Sequence</A>. <A href="#1">[1]</A>
<h3>Example</h3>
<pre>
<A href="List.html">list</A>&lt;int&gt; L;
L.push_front(3);
back_insert_iterator&lt;<A href="List.html">list</A>&lt;int&gt; &gt; ii(L);
*ii++ = 0;
*ii++ = 1;
*ii++ = 2;
<A href="copy.html">copy</A>(L.begin(), L.end(), <A href="ostream_iterator.html">ostream_iterator</A>&lt;int&gt;(cout, &quot; &quot;));
// The values that are printed are 3 0 1 2
</pre>
<h3>Definition</h3>
Defined in the standard header <A href="iterator">iterator</A>, and in the nonstandard
backward-compatibility header <A href="iterator.h">iterator.h</A>.
<h3>Template parameters</h3>
<Table border>
<TR>
<TH>
Parameter
</TH>
<TH>
Description
</TH>
<TH>
Default
</TH>
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<TR>
<TD VAlign=top>
<tt>BackInsertionSequence</tt>
</TD>
<TD VAlign=top>
The type of <A href="BackInsertionSequence.html">Back Insertion Sequence</A> into which values will be inserted.
</TD>
<TD VAlign=top>
&nbsp;
</TD>
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</table>
<h3>Model of</h3>
<A href="OutputIterator.html">Output Iterator</A>.  An insert iterator's set of value types (as
defined in the <A href="OutputIterator.html">Output Iterator</A> requirements) consists of
a single type: <tt><A href="BackInsertionSequence.html">BackInsertionSequence</A>::value_type</tt>.
<h3>Type requirements</h3>
The template parameter <tt>BackInsertionSequence</tt> must be a 
<A href="BackInsertionSequence.html">Back Insertion Sequence</A>.
<h3>Public base classes</h3>
None.
<h3>Members</h3>
<Table border>
<TR>
<TH>
Member
</TH>
<TH>
Where defined
</TH>
<TH>
Description
</TH>
</TR>
<TR>
<TD VAlign=top>
<tt>back_insert_iterator(BackInsertionSequence&amp;)</tt>
</TD>
<TD VAlign=top>
<tt>back_insert_iterator</tt>
</TD>
<TD VAlign=top>
See below.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>back_insert_iterator(const back_insert_iterator&amp;)</tt>
</TD>
<TD VAlign=top>
 <A href="trivial.html">Trivial Iterator</A>
</TD>
<TD VAlign=top>
The copy constructor
</TD>
</TR>
<TR>
<TD VAlign=top>
<pre>
back_insert_iterator&amp; 
operator=(const back_insert_iterator&amp;)
</pre>
</TD>
<TD VAlign=top>
 <A href="trivial.html">Trivial Iterator</A>
</TD>
<TD VAlign=top>
The assignment operator
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>back_insert_iterator&amp; operator*()</tt>
</TD>
<TD VAlign=top>
 <A href="OutputIterator.html">Output Iterator</A>
</TD>
<TD VAlign=top>
Used to implement the <A href="OutputIterator.html">output iterator</A> expression <tt>*i = x</tt>. <A href="#2">[2]</A>
</TD>
</TR>
<TR>
<TD VAlign=top>
<pre>
back_insert_iterator&amp; 
operator=(const BackInsertionSequence::value_type&amp;)
</pre>
</TD>
<TD VAlign=top>
 <A href="OutputIterator.html">Output Iterator</A>
</TD>
<TD VAlign=top>
Used to implement the <A href="OutputIterator.html">output iterator</A> expression <tt>*i = x</tt>. <A href="#2">[2]</A>
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>back_insert_iterator&amp; operator++()</tt>
</TD>
<TD VAlign=top>
 <A href="OutputIterator.html">Output Iterator</A>
</TD>
<TD VAlign=top>
Preincrement.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>back_insert_iterator&amp; operator++(int)</tt>
</TD>
<TD VAlign=top>
 <A href="OutputIterator.html">Output Iterator</A>
</TD>
<TD VAlign=top>
Postincrement.
</TD>
</TR>
<TR>
<TD VAlign=top>
<pre>
output_iterator_tag 
iterator_category(const back_insert_iterator&amp;)
</pre>
</TD>
<TD VAlign=top>
 <A href="iterator_tags.html">iterator tags</A>
</TD>
<TD VAlign=top>
Returns the iterator's category.
   This is a global function, not a member.
</TD>
</TR>
<TR>
<TD VAlign=top>
<pre>
template&lt;class BackInsertionSequence&gt;
back_insert_iterator&lt;BackInsertionSequence&gt;
back_inserter(BackInsertionSequence&amp; S)
</pre>
</TD>
<TD VAlign=top>
<tt>back_insert_iterator</tt>
</TD>
<TD VAlign=top>
See below.
</TD>
</tr>
</table>
<h3>New members</h3>
These members are not defined 
in the <A href="OutputIterator.html">Output Iterator</A> requirements,
but are specific to <tt>back_insert_iterator</tt>.
<Table border>
<TR>
<TH>
Member function
</TH>
<TH>
Description
</TH>
</TR>
<TR>
<TD VAlign=top>
<tt>back_insert_iterator(BackInsertionSequence&amp; S)</tt>
</TD>
<TD VAlign=top>
Constructs a <tt>back_insert_iterator</tt> that inserts objects
   after the last element of <tt>S</tt>.  (That is, it inserts objects
   just before <tt>S</tt>'s past-the-end iterator.)
</TD>
</TR>
<TR>
<TD VAlign=top>
<pre>
template&lt;class BackInsertionSequence&gt;
back_insert_iterator&lt;BackInsertionSequence&gt;
back_inserter(BackInsertionSequence&amp; S);
</pre>
</TD>
<TD VAlign=top>
Equivalent to <tt>back_insert_iterator&lt;BackInsertionSequence&gt;(S)</tt>. <A href="#3">[3]</A>
   This is a global function, not a member function.
</TD>
</tr>
</table>
<h3>Notes</h3>
<P><A name="1">[1]</A>
Note the difference between assignment through a
<tt><A href="BackInsertionSequence.html">BackInsertionSequence</A>::iterator</tt> and assignment through a
<tt>back_insert_iterator&lt;<A href="BackInsertionSequence.html">BackInsertionSequence</A>&gt;</tt>.  If <tt>i</tt> is a valid
<tt><A href="BackInsertionSequence.html">BackInsertionSequence</A>::iterator</tt>, then it points to some particular
element in the <A href="BackInsertionSequence.html">back insertion sequence</A>; the expression <tt>*i = t</tt> 
replaces that element with <tt>t</tt>, and does not change the total number
of elements in the <A href="BackInsertionSequence.html">back insertion sequence</A>.  If <tt>ii</tt> is a valid
<tt>back_insert_iterator&lt;<A href="BackInsertionSequence.html">BackInsertionSequence</A>&gt;</tt>, however, then 
the expression <tt>*ii = t</tt> is equivalent, to the 
expression <tt>seq.push_back(t)</tt>.  That is, it does not overwrite
any of <tt>seq</tt>'s elements and it does change <tt>seq</tt>'s size.
<P><A name="2">[2]</A>
Note how assignment through a <tt>back_insert_iterator</tt> is implemented.
In general, unary <tt>operator*</tt> must be defined so that it returns a
proxy object, where the proxy object defines <tt>operator=</tt> to perform
the insert operation.  In this case, for the sake of simplicity, the
proxy object is the <tt>back_insert_iterator</tt> itself.  That is, <tt>*i</tt> simply
returns <tt>i</tt>, and <tt>*i = t</tt> is equivalent to <tt>i = t</tt>.  You should not,
however, rely on this behavior.  It is an implementation detail,
and it is not guaranteed to remain the same in future versions.
<P><A name="3">[3]</A>
This function exists solely for the sake of convenience:
since it is a non-member function, the template parameters may be
inferred and the type of the <tt>back_insert_iterator</tt> need not be declared
explicitly.  One easy way to reverse a range and insert it
at the end of a <A href="BackInsertionSequence.html">Back Insertion Sequence</A> <tt>S</tt>, for example, is
<tt><A href="reverse_copy.html">reverse_copy</A>(first, last, back_inserter(S))</tt>.
<h3>See also</h3>
<A href="insert_iterator.html">insert_iterator</A>, <A href="front_insert_iterator.html">front_insert_iterator</A>, <A href="OutputIterator.html">Output Iterator</A>,
<A href="BackInsertionSequence.html">Back Insertion Sequence</A>, <A href="Sequence.html">Sequence</A>, <A href="Iterators.html">Iterator overview</A>

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